Field of the Invention
The present invention relates to weather-resistant extruded rubbery articles having on the surface thereof a thin rubbery layer colored in a desired tint and to a process for manufacturing same. More particularly, the present invention relates to weather-resistant extruded articles based on ethylene-propylenediene monomer (referred to hereinafter as EPDM) rubber having on the surface thereof a thin rubbery layer of a smooth or suede-like appearance colored in a desired tint and integrally formed on the substrate as well as a process for the manufacture of such weather-resistant extruded articles wherein EPDM and a colored rubbery compound comprising EPDM and a graft copolymer of EPDM and vinyl chloride are subjected together with a vulcanizing system to extrusion molding followed by vulcanization with or without foaming, and if necessary, the foamed surface of the extruded article is polished with an abrasive.
Description of the Prior Arts
EPDM is an ethylene-propylene-diene terpolymer prepared by introducing into ethylene-propylene copolymer devoid of any polymerizable double bond in a main chain thereof a third component having an unsaturated group (such as a diene monomer) to make the copolymer capable of being vulcanized with sulfur. As EPDM possesses excellent resisting properties to ozone, heat and weathering action, it is widely utilized as a rubbery material, especially for manufacturing various parts of motor vehicles, such as automotive windshield weatherstrip, glass run channel, door sponge rubber and weatherstrip. EPDM rubber used for these parts are colored in black because of compounding with carbon black for enhancing weather-resistance or the like valuable properties. Thus, the color of EPDM rubber used for these auto parts is exclusively black due to the carbon black filler.
In recent years, EPDM rubber articles colored in various kinds of tint have increasingly been required to satisfy users' versatile needs. For manufacturing EPDM rubber colored in various kinds of tint, it is necessary to incorporate EPDM with a variety of colored fillers, for example, calcium carbonate or clay as a white-colored filler in place of carbon black. In addition to needs for versatility in tint of EPDM rubber articles, it is also required for these articles to have a fabric-like or suede-like appearance. For modifying the surface of EPDM rubber articles to have such appearance, it has long been considered to apply a colored fabric sheet onto the surface of the black-colored EPDM rubber substrate or to make planting of colored fibers on the surface of the substrate. However, this requires on the surface of the extruded and vulcanized EPDM rubber substrate a series of complicated and troublesome steps of buffing, washing, application of a binder, application of a fabric sheet (or fiber planting), and drying which necessarily increases the production cost as a whole. Further, it is difficult to apply a binder or fabric uniformly in compliance with the complicated structure of the substrate, thus creating a problem in quality control. An ordinary fiber planting device is already known (U.S. Pat. No. 3,543,721) but application of this art to rubber to obtain a suede-like appearance is not known. It is also expected that a colored EPDM rubber is foamed on the surface thereof after extrusion and vulcanization and the skin of the foam is removed by polishing with an abrasive to obtain a suede-like appearance. For realizing this, it is necessary, as described above, to incorporate EPDM with not only a foaming agent but also a variety of colored fillers or pigments in place of carbon black and to foam EPDM after extrusion.
However, a colored EPDM rubber free from carbon black is poor in weather resistance. Thus, a non-staining age-resistor, an UV-absorbing agent and a light stabilizer have been incorporated singly or in combination into the colored EPDM rubber to overcome the above disadvantage but without the expected results.
On the other hand, application of a paint or the like coloring agent onto the surface of carbon black-incorporated EPDM rubber is already proposed as a means for coloring the black EPDM rubber. In this case, however, such paint generally forms a rigid film on the surface of the rubber, thus deteriorating flexibility of the rubber. Although some paints leave a flexible film, such paints are generally inferior in weather resistance. Thus, many problems to be solved are involved in such a direct coloring method for carbon black-incorporated EPDM rubber.
Thus, any successful result has not yet been reported hitherto in the above mentioned various methods with respect to coloring of carbon black-incorporated EPDM rubber.
Reported recently for coloring EPDM rubber is a chemical modification method wherein the surface of EPDM rubber is halogenated and a paint is then applied to the surface (U.S. Pat. No. 3,935,329). However, at least one of the advantageous properties of carbon black-incorporated EPDM rubber is damaged even in the case of using this chemical method. In general, a layer of a coloring material applied onto black-colored EPDM rubber tends to cause delamination or damage the inherent useful properties, e.g. weather-resisting property, flexibility, etc., of carbon black-incorporated EPDM rubber. On the other hand, incorporation of EPDM rubber with a coloring filler in place of carbon black has already proved to be undesirable in view of serious deterioration of the useful properties of EPDM rubber. Thus, any layer or film applied onto carbon black-incorporated EPDM rubber for the purpose of coloring should be thin enough lest the inherent useful properties of the rubber should be damaged.
Accordingly, there is a great demand for developing a new method for coloring carbon black-incorporated EPDM rubber without deterioration of the inherent useful properties of the rubber.